A fixed date for Easter has been elusive, despite previous attempts to produce one since the Council of Nicea first came up with a complex formula in 325 AD.

That Council of Christian leaders was convened by the Roman Emperor Constantine I to gain consensus throughout Christendom, but unfortunately these good intentions were dashed by the schism centuries later between the Orthodox and Western Churches, and the split between the Roman Catholics and Protestants.

Nevertheless, the ancient leaders did manage to agree about Easter, but their formula is not for the faint-hearted.

Easter Day is celebrated each year on the Sunday, following the full moon that falls on or after the Spring Equinox. Simple, isn't it?

This means that Easter Day can fall any time between the middle of March or April. This year it's on March 27, next year April 16, and in 2018 it's on April 1 - which will have nothing to do with All Fools' Day.

The majority of people would welcome a fixed date for Easter, which would help with school and family holidays, as well as commercial life.

There would be no loss of Christian solidarity if the Churches could all celebrate Easter on the same day.

However, there are an awful lot of different Christian denominations, as I found out when reporting on the funeral of Pope John Paul II. Church leaders from denominations I had never even heard of paid tribute to the departed Pope in his plain wooden coffin.

There is another complication, in that Easter is closely connected to the Jewish Passover, which itself is a moveable feast. So don't expect an agreement on a fixed Easter any time soon, though it will come eventually.

Meantime, Dr Welby and his fellow Primates have a more immediate problem on their minds as they try to prevent a schism in the Anglican Communion over same-sex marriage.

It is a sensitive issue, and many people have been deeply hurt, hence the apology from Dr Welby for the way the Church has historically treated same-sex couples.

The latest suspension of the US Episcopal Church for three years because of its support for same-sex marriage is an attempt to create some breathing space.

So too is this week's issue by the Church of Ireland of a booklet about Conversations on Human Sexuality.

At the very least, the Anglicans deserve credit for facing up to this thorny issue.

The Presbyterian Church in Ireland has not won many friends over this topic, and it seems to deal with same-sex marriage like a rugby player tackling an opponent to the ground and then pinning him down. It is an extremely difficult issue to solve, but the conservative Presbyterians will find out soon enough that taking a hard-line on dissent is not the best way forward.

Subtlety, however, is not always their strongest suit, as they have shown time and again.